Quintus was a good friend and Subordinate General to Roman General Maximus Decimus Meridius.
Quintus was a friend of General Maximus, and he was his Second-in-Command General. He advised Maximus to move the Catapults back to avoid them being a threat to the cavalry. However, Maximus ordered his catapults at the same range as they were, saying the range was fine. After a gory and intense battle, Quintus and Maximus met again at a victory party made by Roman Emperor Marcus Aurelius. The two embraced each other, and loved to know that they were both alive. However, when Marcus Aurelius was murdered by his son, Prince Commodus, Quintus sided with the usurper by following through the execution order of Maximus, adding that his family would see him in the afterlife.
Quintus later redeemed himself to Maximus when Commodus asked for a sword as Quintus refused to give him one, along with telling the guards to sheathe their swords. When Commodus was killed by Maximus, who had escaped the execution and was seeking revenge for Commodus' order to kill his family and burn his farm, Quintus asked for the last wish of his dying old friend. Maximus died in Princess Lucilla's arms, and Quintus along with Lucius, Gracchus, the guards, and the slaves helped carry the body of his deceased friend to the grave while Commodus' body was left on the ground to rot.
The movie's Quintus was likely based on Quintus Laetus, a praetorian prefect who were appointed to the role by the historical Emperor Commodus. He was also one of the key conspirators who assassinated Commodus afterwards.